X-Wings and the Rectangle Rule for Solving Medium to Hard Sudoku Puzzles

Lesson #X-wing10: patterns appear often and can be used as a Sudoku solving strategy to eliminate candidates. This quick Sudoku lesson explains how to recognize the X-wing pattern, also known as the rectangle rule, and how to use it as a strategy to solve Medium and Hard level Sudoku puzzles. Keep practicing, and learn something new every day!
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[@hilaydt]

I've watched many other videos and read tutorials on how to do X wings and I never understood until I watched your breakdown. Thanks so much for the clear explanation!

[@majaber1]

me too

[@rameshramasamy21]

Me too

[@leemelbourne-weaver4337]

ME too

[@soniaperezcaceres3935]

Same!!!!

[@RandomThingsEn]

SAME! the other tutorials didn't really mention the rows part

[@rameshramasamy21]

Thank you for clearly explaning. I was not able to resolve a sudoku and didn't sleep for 5 days. Your video rescued me.

[@jballenger9240]

The clearest explanation I’ve heard of the X-wing. Thank you m

[@StephenRahrig]

Why are you calling it a 2 x 2

[@flynn1a]

I have watched several x wing videos and couldn’t get the gist of what they were saying. But you made it so simple and so obvious! Thank you!!!!

[@r.mcd2921]

Thank you - this was the first explanation that made sense to me.

[@Omoplata183]

I finally get it, thank you for this!!

[@kalpanasarkar9331]

Best explanation of x wing I've come across so far

[@JonJacks]

Okay wow! I've seen the X wing so many times and never thought there was a strategy. THANK. YOU.

[@rajeshwarichauhan4257]

I had been trying to understand this pattern from many videos ...but u explained it so clearly...i got it in a minute..❤🌻

[@LearnSomethingNewEveryDay]

Glad to hear that, thanks for the comment!

[@martinaperez9594]

Such an useful trick! I'll implement it, thanks!

[@mattnorton3285]

Apologies if I'm missing an obvious implication, but for the part of the video from 1:26 to 1:34, why must the 2 in column 7 be the correct one? Why couldn't the 2 in column 8 be correct? (and same question for the 2 in column 9 in row C)

[@fire285]

Hey, the square is the only option for these numbers. We know 2 must be present in column 4 and 7 and that all other options in column 4 and 7 cannot hold a two. As a generalized rule, if a square exists where either a row or column requires a number to be in the square then both the row and column require the numbers to be in the square.

[@love4music25]

can you expand further? @@fire285 I still didnot get it

[@hebum]

I was wondering about the same thing but if you look at the column 7 , 2 can be placed in only in the A or C rows for that column so we wouldn't even mark 8A or 9C as possibilities 🤦‍♂

[@SmartHobbies]

Great straightforward explanation of X-wings. I always found it interesting that 2x2 are called “wings” where 3x3, 4x4, etc. all are “fish”. I look forward to watching more of your content.

[@LearnSomethingNewEveryDay]

Thanks Smart Hobbies.....yes it is interesting how these are called exotic fish names.....thanks for your support, I appreciate it! Good luck with your channel, it looks interesting....I just subbed!

[@faisalrezhaRakhman]

Easy to understand, thanks alot.

[@ruatoomey9107]

Top class, thank you

[@muhammadzakyyahya1625]

I still don't understand the first example..

[@divermike8943]

Why do you say it is a 2x2 retangle? The first example with the 4s is three rows by four columns. So is the second example with the 2s. Does the size of the retangle even matter?

[@DiederdirkDusty]

The size doesn't matter, only that 2 colomns/rows contain 4 cells where a candidate can go and form a x-pattern.

[@claudegiguere8731]

straight to the point and excellent explanations 👍 Thanks a lot !!!

[@kskaliprasadkotagal6468]

Thanks for sharing this idea of elimination

[@timothymarchant]

so what happens with the annotated number outside the rectangle but in the same box but it's in the middle/ For example if Cell B9 had a 2 candidate as well would that justify removing that candidate?

[@brittanydrake7643]

I was wondering the same thing

[@BillSmith-bd1yv]

Sorry, I don't understand why we would call an area of 4 squares by 3 a "2x2 rectangle" and if it really was 2x2 then wouldn't it be a square? Asking for clarification because I can see lots of potential candidate configurations, but they can't all be usable. Thanks in advance.

[@epistemophiliac5334]

I don't understand why you can eliminate the 2s in A8 and C9. The solutions for 2 could easily be A4/C9 or A8/C4. Why does candidates forming a rectangle mean you can eliminate every other candidate in their rows?

[@anonym6891]

In my opinion this explanation has errors.

[@cineeleo]

Hi, late answer, but anyway: if you try any of your possible variants, A4/C9 or A8/C4, you can observe that in column 4 and in 7 there is no cell to put the 2. That's because in column 4 and 7, the 2 can be put only in A2/C7 or A7/C2. Hope this helps.

[@aubreymaichi4600]

omg finally a vid that's easy for me to understand😢

[@robertvolm3609]

So, does this mean that a "X" is always a 3 square by 4 square grid? Can it be 4 squares by 5 squares? Or anything different?

[@yennisutedjo4173]

Nice explanation

[@scorbett4370]

Is this rectangle referred to as a 2 by 2 because it involves 2 Blocks AND 2 Rows AND 2 Columns? Thank you for the video.

[@NightSovereign]

what does 2x2 stand for? And why is the rectangle 4x3 is called so?

[@hieutv.thebattlecats]

very nice

[@kevinklise7036]

A good explanation. However, I need to ask for a couple points of clarification. If the particular number being used as the four corners of the rectangle (in this video, it was a "2"), then all the other 2's in that row can be eliminated. Does that include the 2's that are ONLY OUTSIDE the rectangle? Or can it include the 2's (if any) BETWEEN the four corners of the rectangle?

[@eugenetswong]

Yes, between and outside. I remember it this way: it doesn't matter how you find the rectangle; eliminate all of them in the columns and rows, except the 4 corners.

[@kenjohnson4645]

Would if be possible to get the name or link of the Sudoku program that you use in your tutorials as I wanted a program that would allow the user to take advantage of or have the ability to use a "Red X" or similar markings.

[@dras227]

how it is an X pattern? if 2 in A4 is true, then both 2's in C7 and C9 can be true

[@MacXpert74]

They can't because you need to look at the columns in this case. In both column 4 and column 7 the ONLY 2's are in row A & C, therefore forming a X-wing, this then allows to eliminate any other 2's in those rows. Because if you would place the 2 in C9, you can't place any 2's anywhere in column C7, which would make the Sudoku invalid.

[@believeinaction]

Love from India 🤩🤩🤩🔥🔥

[@lindac6147]

I’m confused . You state when referring to the first example ( ~3:00) with “2” that they are identified to be part of an x wing if the candidate only appears twice. However “2” appears three times on row A?

[@groslou9997]

You have to think in columb

[@groslou9997]

Column 7

[@diramaking4302]

@@groslou9997 Thanks bro. This is what was confusing me for so long. I am quite good at sudoku and I was confused how I am not understanding what everyone is calling a simple technique. I can't believe I was overlooking this... I have been using this for so long without realising it...

[@elkabat5205]

​@@groslou9997okay but then I don't need the X-wing right? If I can see that no other 2 can appear in column 7 then its obvious that rows 1 or 3 must have a 2. Am I missing something?

[@robertnutt4944]

Hi, how does this work in a 16 x 16 Sudoku? Any different?

[@albythegreat4648]

Still unsure if that's really a fact you can eliminate the other numbers in the same group or not. Couldn't the 2 still possibly be in the other 2 spots?

[@eyefeelpineal4079]

Yeah that's what I'm struggling with

[@sudharshank8256]

This method doesn't work. I wonder how this video got so many positive comments

[@garondes1]

I just don’t get it, there are other numbers that repeat also like the 6 7 and 8, why don’t they form an X wing? why choose the 2 in particular?

[@danielkirby3079]

I’m sorry, I listened to the video several times and I never understood where you explained which was the correct 2. One of the comments was between 1:26-1:34 of your video but I didn’t catch it. I did hear where you spoke of eliminating other 2’s in actual rows but couldn’t discern which 2 you picked in the x-wing. Most of the comments seem to be happy with your explanation so I am sure it’s just my ADD or lack of understanding. Could you please explain how you picked the correct 2 in the x-wing and not how you eliminated the other 2’s?

[@oksanaball6494]

Why did you pick number 2 and not 6,7 or 8? Number 4 and not 5, 6, 7 or 8?

[@royalbloodedmutt]

Finally an explanation that makes sense!!! Bless you.

[@kennethwoodby4528]

what does it mean when we say that a cell cant see eachother

[@LearnSomethingNewEveryDay]

these are also called "peer" cells, they are either in the same block, row, or column, then they "see" each other. Hope that helps.

[@179Kreator]

Hello, I applied it in a an expert sudoku and it didn’t work

[@aninterviewwith...1702]

I'll have to come back to this one. I still don't get it.

[@Fenar_]

Can someone explain why the twos in column 8 and 9 wouldn't be a possibility?

[@RusNad]

Because column 7's twos have to be in the top right box, that already eliminates the twos in column 8 and 9

[@RusNad]

But I think even if they were across different boxes, the x-wing means that if A8 was two, then C4 and C7 would both have to be two, which is impossible.

[@groslou9997]

What is the method to resolve this sudoku please ? May you resolve fully this sudoku in an other vidéo for exemple plz ?

[@kaneshoots]

I still can't understand why you choose the 2's in the beginning as there are also, 6s 7s 8s

[@alg4943]

Does anyone ever find more than one X-Wings in a puzzle?

[@elgiztaghiyev3194]

There only "E and H" has 2 it means automatically A and C has to have 2 you explain more harder than I think

[@MikeKey91]

Everytime I use this I get a mistake. Still no clue.

[@sontungo1505]

Sorry but I think THIS IS NOT X-wings technique. At example 1, in column 7, there only 2 possibilities for number 2 (A7 & C7) and they also in the same Square 3. Therefore in Square 3, we can eliminate the others number 2 at A8 & C9. There's no need to use 2 number 2 in column 4 as she called this X-wings. (The similiar thing at example 2...). I think she should use other examples for this technique.

[@juliafullbusterdododotanmh6837]

I agree

[@kvothe2144]

This video: Let me repeat myself 30 times.

[@ted5669]

It’s not a 2x2 rectangle, that would be a square

[@betmenizorahovice4843]

this looks like cheating to be honest, x wings is too powerful and much more easier to spot that xy wings

[@ramanaross]

Sorry, incorrect. This is NOT and X Wing pattern. X Wing logic requires the four setup numbers to be in four different blocks. Your analysis is false because ... if the 2 in Block 2 Row 1 is true, then either of the 2's in Block 3 Row 3 can be true. Likewise, if the 2 in Block 2 Row 3 is true, then either of 2's in Block 3 Row 1 can be true. No eliminations can be made. What you have shown is a setup for a possible Unique Rectangle analysis which requires the four numbers to be in only two blocks.

[@eitradder]

This is wrong

[@steveloudon7491]

Why do you say that

[@sudharshank8256]

​@@steveloudon7491because she ignored other "2" possibilities in the 3rd box